Merge pull request #1060 from ethereum/JustinDrake-patch-20

Cleanup int_to_bytes

scripts/phase0/build_spec.py

@@ -15,16 +15,9 @@ from typing import (
 from eth2spec.utils.minimal_ssz import *
 from eth2spec.utils.bls_stub import *
 
-""")
-    for i in (1, 2, 3, 4, 8, 32, 48, 96):
-        code_lines.append("def int_to_bytes%d(x): return x.to_bytes(%d, 'little')" % (i, i))
-
-    code_lines.append("""
-
 # stub, will get overwritten by real var
 SLOTS_PER_EPOCH = 64
 
-
 Slot = NewType('Slot', int)  # uint64
 Epoch = NewType('Epoch', int)  # uint64
 Shard = NewType('Shard', int)  # uint64

specs/core/0_beacon-chain.md

@@ -75,7 +75,7 @@
         - [`compute_committee`](#compute_committee)
         - [`get_crosslink_committee`](#get_crosslink_committee)
         - [`get_attesting_indices`](#get_attesting_indices)
-        - [`int_to_bytes1`, `int_to_bytes2`, ...](#int_to_bytes1-int_to_bytes2-)
+        - [`int_to_bytes`](#int_to_bytes)
         - [`bytes_to_int`](#bytes_to_int)
         - [`get_total_balance`](#get_total_balance)
         - [`get_domain`](#get_domain)
@@ -194,8 +194,8 @@ These configurations are updated for releases, but may be out of sync during `de
 | `GENESIS_SLOT` | `0` |
 | `GENESIS_EPOCH` | `0` |
 | `FAR_FUTURE_EPOCH` | `2**64 - 1` |
-| `ZERO_HASH` | `int_to_bytes32(0)` |
+| `ZERO_HASH` | `b'\x00' * 32` |
-| `BLS_WITHDRAWAL_PREFIX_BYTE` | `int_to_bytes1(0)` |
+| `BLS_WITHDRAWAL_PREFIX` | `0` |
 
 ### Time parameters
 
@@ -830,7 +830,7 @@ def generate_seed(state: BeaconState,
     return hash(
         get_randao_mix(state, epoch + LATEST_RANDAO_MIXES_LENGTH - MIN_SEED_LOOKAHEAD) +
         get_active_index_root(state, epoch) +
-        int_to_bytes32(epoch)
+        int_to_bytes(epoch, length=32)
     )
 ```
 
@@ -851,7 +851,7 @@ def get_beacon_proposer_index(state: BeaconState) -> ValidatorIndex:
     i = 0
     while True:
         candidate_index = first_committee[(epoch + i) % len(first_committee)]
-        random_byte = hash(seed + int_to_bytes8(i // 32))[i % 32]
+        random_byte = hash(seed + int_to_bytes(i // 32, length=8))[i % 32]
         effective_balance = state.validator_registry[candidate_index].effective_balance
         if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte:
             return candidate_index
@@ -888,10 +888,10 @@ def get_shuffled_index(index: ValidatorIndex, index_count: int, seed: Bytes32) -
     # Swap or not (https://link.springer.com/content/pdf/10.1007%2F978-3-642-32009-5_1.pdf)
     # See the 'generalized domain' algorithm on page 3
     for round in range(SHUFFLE_ROUND_COUNT):
-        pivot = bytes_to_int(hash(seed + int_to_bytes1(round))[0:8]) % index_count
+        pivot = bytes_to_int(hash(seed + int_to_bytes(round, length=1))[0:8]) % index_count
         flip = (pivot - index) % index_count
         position = max(index, flip)
-        source = hash(seed + int_to_bytes1(round) + int_to_bytes4(position // 256))
+        source = hash(seed + int_to_bytes(round, length=1) + int_to_bytes(position // 256, length=4))
         byte = source[(position % 256) // 8]
         bit = (byte >> (position % 8)) % 2
         index = flip if bit else index
@@ -934,9 +934,12 @@ def get_attesting_indices(state: BeaconState,
     return sorted([index for i, index in enumerate(committee) if get_bitfield_bit(bitfield, i) == 0b1])
 ```
 
-### `int_to_bytes1`, `int_to_bytes2`, ...
+### `int_to_bytes`
 
-`int_to_bytes1(x): return x.to_bytes(1, 'little')`, `int_to_bytes2(x): return x.to_bytes(2, 'little')`, and so on for all integers, particularly 1, 2, 3, 4, 8, 32, 48, 96.
+```python
+def int_to_bytes(integer: int, length: int) -> bytes:
+    return integer.to_bytes(length, 'little')
+```
 
 ### `bytes_to_int`
 
@@ -966,7 +969,7 @@ def get_domain(state: BeaconState,
     """
     epoch = get_current_epoch(state) if message_epoch is None else message_epoch
     fork_version = state.fork.previous_version if epoch < state.fork.epoch else state.fork.current_version
-    return bytes_to_int(fork_version + int_to_bytes4(domain_type))
+    return bytes_to_int(fork_version + int_to_bytes(domain_type, length=4))
 ```
 
 ### `get_bitfield_bit`
@@ -1837,7 +1840,7 @@ def process_transfer(state: BeaconState, transfer: Transfer) -> None:
     # Verify that the pubkey is valid
     assert (
         state.validator_registry[transfer.sender].withdrawal_credentials ==
-        BLS_WITHDRAWAL_PREFIX_BYTE + hash(transfer.pubkey)[1:]
+        int_to_bytes(BLS_WITHDRAWAL_PREFIX, length=1) + hash(transfer.pubkey)[1:]
     )
     # Verify that the signature is valid
     assert bls_verify(transfer.pubkey, signing_root(transfer), transfer.signature, get_domain(state, DOMAIN_TRANSFER))

specs/core/1_shard-data-chains.md

@@ -180,7 +180,7 @@ def get_shard_proposer_index(state: BeaconState,
                              slot: Slot) -> ValidatorIndex:
     # Randomly shift persistent committee
     persistent_committee = get_persistent_committee(state, shard, slot)
-    seed = hash(state.current_shuffling_seed + int_to_bytes8(shard) + int_to_bytes8(slot))
+    seed = hash(state.current_shuffling_seed + int_to_bytes(shard, length=8) + int_to_bytes(slot, length=8))
     random_index = bytes_to_int(seed[0:8]) % len(persistent_committee)
     persistent_committee = persistent_committee[random_index:] + persistent_committee[:random_index]
 

specs/light_client/sync_protocol.md

@@ -146,7 +146,7 @@ def compute_committee(header: BeaconBlockHeader,
     ]
     def get_switchover_epoch(index):
         return (
-            bytes_to_int(hash(validator_memory.earlier_period_data.seed + int_to_bytes3(index))[0:8]) %
+            bytes_to_int(hash(validator_memory.earlier_period_data.seed + int_to_bytes(index, length=3))[0:8]) %
             PERSISTENT_COMMITTEE_PERIOD
         )
 

test_generators/shuffling/main.py

@@ -15,7 +15,7 @@ def shuffling_case(seed: spec.Bytes32, count: int):
 
 @to_tuple
 def shuffling_test_cases():
-    for seed in [spec.hash(spec.int_to_bytes4(seed_init_value)) for seed_init_value in range(30)]:
+    for seed in [spec.hash(spec.int_to_bytes(seed_init_value, length=4)) for seed_init_value in range(30)]:
         for count in [0, 1, 2, 3, 5, 10, 33, 100, 1000]:
             yield shuffling_case(seed, count)